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Updated: Aug 14, 2026

Muscle Receptor Organs in the Crayfish Abdomen: A Student Laboratory Exercise in Proprioception
Published on: November 19, 2010
Cournand lecture: Mechanical action of the abdominal muscles
Abstract:
The abdominal muscles, by causing a rise in abdominal pressure and a cranial displacement of the diaphragm, 1--deflate the lungs (minimize the increase in FRC which normally occurs when adopting the standing posture), 2--exert an expanding force on the lower rib cage, which may counterbalance or even dominate the insertional (expiratory) force they exert on the lower ribs by way of their insertions, 3--improve the pressure-generating ability of the diaphragm. In addition, because they prevent the diaphragmatic dome from descending during inspiration, they also improve the rib cage expanding action of the diaphragm.
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